It is known to prepare borate solutions with a high boron content using organic solvents. Thus U.S. Pat. No. 4,332,609 describes a method of fertilising plants in which the reaction product of a boric acid compound with an alkanolamine or aliphatic polyamine, in particular monoethanolamine, is applied to plants. The reaction products are water-soluble and thus can be dissolved in water for application to crops. The production of the monoethanolamine reaction products for example, adds to the cost of the boron to be applied to the crops.
Using an alternative organic solvent, U.S. Pat. No. 4,572,733 describes a so-called storage-stable concentrate formed by making a solution of a first boron compound in a water-miscible glycol solvent and then dispersing fine particles of a second boron compound in the solution. For use, the storage-stable concentrate is diluted with water and applied to crops.
Aqueous borate suspension formulations have been proposed for the treatment of timber. Thus AU-A-574389 proposes the use of a preservative composition comprising a colloidal micro-crystalline suspension of boron salts and a thickening agent, which serves to maintain the stability of the suspension. Similarly EP-A-0289317 describes timber preservative compositions comprising a boron-containing preservative, which may be a micro-crystalline suspension, e.g. 10 to 30 microns, and a thickening agent such as the polysaccharide xanthan gum in a preferred amount of 0.25 to 3.0% by weight. These compositions are obtained by forming, with heating, a borate solution, cooling rapidly to obtain crystals and adding thickening agent to maintain the crystals in suspension. Such compositions are stiff and pasty.
The combination of borates and xanthan gum has also been described in connection with other applications. For example, UK Patent No. 1,395,502 discloses herbicidal compositions containing gelling agent compounds such as a combination of xanthan gum and a borate salt. U.S. Pat. No. 3,326,733 discloses a gelled explosive containing water, Xanthamonous hydrophilic colloid, borax and a monovalent water-soluble explosive salt. Japanese Patent Application No. S61-158907 describes compositions for a mold and mildew removing agent that contains an organic polymer, such as xanthan gum, guar gum, locust bean gum, casein or other similar materials, in combination with a peroxide compound, such as hydrogen peroxide or a hydrogen peroxide producing compound such as sodium perborate monohydrate or sodium perborate tetrahydrate.